The subject matter relates generally to transducers that are configured to be fully submerged within a liquid and connected to the external environment through a cable.
Submersible transducers are used to monitor conditions or qualities of a liquid. Submersible transducers may include a housing where a sensor is held and a cable that provides a communication line and power supply for the sensor. For submersible pressure transducers, the sensor is a pressure sensor and the cable may, optionally, include a venting tube for detecting an atmospheric pressure of the external environment. Submersible pressure transducers may be used to monitor ground-water levels in aquifers or deep wells, waste-water levels at different stages of treatment, and surface-water levels in canals or tanks. Other liquids that may be monitored by submersible transducers include industrial chemicals, natural gas liquids (NGLs), and corn oil.
Submersible transducers are often located within the liquid for an extended period of time (e.g., days, weeks, months or years) and can experience extreme conditions, such as extreme pressures and temperatures. For these reasons, submersible transducers can be vulnerable to fluid penetration, which can affect measurements and lead to transducer failure. The monitored liquid can penetrate the submersible transducer by seeping through interfaces where the cable and housing connect. Moisture in the external environment can condense within the venting tube or within the housing. In addition, the cable jacket for submersible pressure transducers is often polyurethane. Polyurethane has a relatively high water-absorption rate relative to other materials.
To minimize fluid penetration through the interfaces, manufacturers have used O-rings, welded seals, potting material, sealed strain-relief, and cable glands. In some transducers, the housing that surrounds the sensor may be disposed within a separate outer housing. Desiccants and water-resistant gels and tapes have also been disposed within the housing to increase the life span of the submersible transducer. For transducers that utilize venting tubes, desiccant cartridges, polytetrafluoroethylene (PTFE) hydrophobic membranes, and aneroid bellows can be connected to the venting tubes. To minimize fluid ingress through the cable jacket, manufacturers have used water-absorbing tape and silicone gels along a length of the cable. Such fillers, however, add cost and complexity to the manufacturing process. Although the above methods can be effective, fluid penetration remains a challenge and, in many cases, is the primary reason for a shortened life span.
Accordingly, there is a need for a submersible transducer that impedes fluid penetration.